X-Ray Films of the Skull

Skull films were once the mainstay of initial diagnostic imaging of a patient with a suspected intracranial mass, but are no longer necessary in the majority of cases. Some abnormalities that affect the appearance of the skull base or calvarium, such as hyperostosis secondary to a meningioma or bone remodelling from a slowly growing tumor, may be seen on x-ray films but are better detected with CT. Furthermore, the extent of involvement is more precisely defined using CT, particularly at the skull base. Intracranial calcification is also shown with greater sensitivity and more precise localization using CT.

High-resolution CT should always be used in instances where conventional x-ray tomography would have been considered previously. CT provides better definition of bone and soft tissue along specific anatomic planes and it allows better definition of small anatomic structures such as skull base foramina and temporal bone anatomy. Additionally, CT exposes the patient to much lower doses of radiation when compared to x-ray tomography.

When an overview of skull anatomy is needed for planning an operative approach, in most cases the lateral scout image of the skull obtained at the time of CT together with the axial CT bone images provide all of the information that is needed. Only in a small minority of cases is skull imaging of value preoperatively.

Skull films have declined markedly in importance and have now been relegated to a secondary diagnostic technique in the work-up of patients with intracranial tumors. The reasons for this change are many. First, literature reviews in large series of patients have shown that skull films obtained in patients who present with symptoms suggestive of an intracranial abnormality demonstrate findings related to the intracranial pathology in only a small percentage of cases. In a selected group of 136 patients with proven intracranial tumor, only 17.6 percent showed positive findings on plain radiography of the skull. Second, the findings seen on skull films are all indirect findings associated with a mass that can be directly visualized with CT. Third, bony changes in the skull base and calvarium, intracranial calcification, and midline shift are all better evaluated with CT. Finally, and probably most compelling, any patient presenting with symptoms suggesting an intracranial neoplasm will still require CT or MRI regardless of the skull film findings.

Nevertheless, it is important to recognize skull film abnormalities suggestive of an intracranial mass, because they are occasionally seen on skull films obtained for unrelated reasons. Such findings include demineralization of the dorsum sellae secondary to increased intracranial pressure, cranial hyperostosis, bone erosion, abnormal intracranial calcification, and midline shift of a calcified pineal gland.